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    乙醇溶液提取-液液萃取置换-气相色谱-质谱法测定咖啡饮品中3种糠醛类化合物的含量

    Determination of 3 Furfural Compounds in Coffee Beverages by Gas Chromatography-Mass Spectrometry with Ethanol Solution Extraction and Liquid-Liquid Extraction Displacement

    • 摘要: 提出了一种用于测定咖啡豆(粉)、纯速溶咖啡、多合一速溶咖啡、咖啡饮料中糠醛、5-甲基糠醛和5-羟甲基糠醛含量的方法。样品经粉碎后,加入50%(体积分数)乙醇溶液作为提取溶剂,10%(质量分数)碳酸钠溶液作为碱性处理剂,于40 ℃超声提取。提取液中3种糠醛类化合物用乙腈进行液液萃取,以降低水相提取液对色谱柱的损伤及其中的杂质对测定的影响。加入20 μL含13C6-5-羟甲基糠醛和糠醛-d4均为10.0 mg·L−1的混合内标溶液,涡旋混匀,离心后,取出上清液置于含C18散装填料100 mg、DSC-SCX强阳离子交换固相萃取散装填料50 mg、无水硫酸镁200 mg的QuEChERS净化管中,涡旋混匀,离心,上清液供气相色谱-质谱法测定。在HP-INNOWAX弹性石英毛细管色谱柱上以程序升温条件分离,电子轰击离子源电离,选择离子监测模式检测,内标法定量检测上述上清液中3种糠醛类化合物。结果显示:3种糠醛类化合物和对应的内标质量浓度比值在0.050~9.92 mg·L−1内和定量离子峰面积比值呈线性关系,糠醛、5-甲基糠醛、5-羟甲基糠醛的检出限为0.002,0.002,0.003 mg·kg−1。以3种糠醛类化合物检出量较低的咖啡豆粉样品作为基质进行两个浓度水平的加标回收试验,回收率为94.0%~107%,测定值的相对标准偏差(n=6)为0.70%~2.2%。方法用于32份实际样品的分析,均检出了3种糠醛类化合物,其中纯速溶咖啡样品中5-羟甲基糠醛平均检出量最高。

       

      Abstract: A method for determination of furfural, 5-methylfurfural, and 5-hydroxymethylfurfural in coffee beans (powder), pure instant coffee, all-in-one instant coffee, and coffee-flavored drinks was proposed. After the sample was crushed, the 50% (volume fraction) ethanol solution was added as an extraction solvent, and the 10% (mass fraction) sodium carbonate solution was added as an alkaline treatment agent. The mixture was extracted by ultrosound at 40 ℃. Three furfural compounds in the extract were replaced by liquid-liquid extraction using acetonitrile, to reduce the damage of the aqueous extract to liquid chromatographic column and the effect of impurities on the determination. A mixed internal standard solution containing both 13C6-5-hydroxymethylfurfural and furfural-d4 at a mass concentration of 10.0 mg·L-1 was added, and the solution was mixed well by vortex and centrifuged. The mixed solution was placed into a QuEChERS purification tube containing 100 mg of C18 bulk filler, 50 mg of DSC-SCX strong cation exchange solid-phase extraction bulk filler, and 200 mg of anhydrous magnesium sulfate. The mixture was mixed well by vortex, and centrifuged, and the supernatant was determined by gas chromatography-mass spectrometry. Three furfural compounds in the obove supernatant were separated on an HP-INNOWAX elastic quartz capillary chromatography column under programmed temperature conditions, ionized by electron impact ion source, detected by selected ion monitoring mode, and quantitatively detected by the internal standard method. It was shown that linear relationships between values of the mass concentration ratios and quantitative ion peak area ratios of 3 furfural compounds to their corresponding internal standards were kept in the range of 0.050-9.92 mg·L-1, with detection limits of 0.002, 0.002, 0.003 mg·kg−1 for furfural, 5-methylfurfural, and 5-hydroxymethylfurfural, respectively. Coffee bean powder samples with low detection amounts of 3 furfural compounds were used as matrices for 2 concentration levels of spiked recovery tests, giving recoveries in the range of 94.0%-107% and RSDs (n=6) of the determined values in the range of 0.70%-2.2%. The proposed method was used for the analysis of 32 actual samples, 3 furfural compounds were detected, and average detection amounts of 5-hydroxymethylfurfural in pure instant coffee samples were highest.

       

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